1. Technical Field of the Invention
The present invention relates to a mounting arrangement for a lens which permits adjustment during assembly of a camera. The invention is particularly, but not exclusively, applicable to the manufacture of small, inexpensive solid state cameras for use in products such as camera phones.
2. Description of Related Art
It is known to provide an image sensor or camera assembly comprising a solid state single chip image sensor and a lens, in which the lens can be adjusted in position during manufacture to achieve optimal focus of the image on the image sensor surface. Typically, the lens is mounted in a lens barrel which has a screw-threaded engagement with a lens mount, and an apparatus adjusts the focus by relative rotation until an optimal focus of a test image is achieved, as judged by an evaluation circuit. The lens barrel may then be locked relative to the chip holder, for example by bonding.
It has been found that after such adjustment a proportion of sensors suffer from unacceptable image quality because of artifacts in the output image. We have established that one cause of this arises from small particles being dislodged from the surfaces of the screw-threaded engagement and lodging on the image sensor surface, or on an optical element (for example, an infrared IR filter) overlying the image sensor surface. Any sensors or cameras suffering from this problem have to be discarded, with consequent increase in the average cost of acceptable sensors.
There is a need in the art to address this problem.